1. Field of the Invention
The present invention relates to methods for producing an L-amino acid using a coryneform bacterium. L-amino acids are industrially useful as additives for animal feeds, ingredients for seasonings, food, and drinks, as well as in amino acid infusions, and so forth.
2. Brief Description of the Related Art
L-amino acids are industrially produced by, for example, fermentation using various microorganisms having an L-amino acid-producing ability. Examples of bacterial strains useful in fermentation methods for producing L-amino acids include, for example, a wild-type microorganism (wild-type strain), an auxotrophic strain derived from a wild-type strain, a metabolic regulation mutant strain derived from a wild-type strain that is resistant to one or more various drugs, and a strain having characteristics as both an auxotrophic strain and metabolic regulation mutant strain.
Further, in recent years, microorganisms in which an L-amino acid-producing ability is improved by recombinant DNA techniques are used for the L-amino acid production. Examples of methods for improving an L-amino acid-producing ability of a microorganism include, for example, enhancing the expression of a gene coding for an L-amino acid biosynthetic enzyme (U.S. Pat. Nos. 5,168,056 and 5,776,736), and enhancing inflow of a carbon source into an L-amino acid biosynthesis system (U.S. Pat. No. 5,906,925).
Escherichia coli has at least two kinds of inorganic phosphate uptake systems (R. M. Harris et al., Journal of Bacteriology, September 2001, pp. 5008-5014). One is the low-affinity inorganic phosphate transporter (Pit) system, and the other is the high-affinity phosphate-specific transporter (Pst) system. Known genes encoding protein products in the Pit system include the pitA gene and the pitB gene. Known genes encoding protein products in the Pst system include the pstSCAB genes. The protein products of the pstSCAB genes form a complex to function as the Pst system. However, the relation between the activities of these phosphate transporters and L-amino acid production has not been previously reported.